A woman who pleaded guilty in 2004 to strangling her girlfriend and dumping her body at Kelley Point Park may not have been the killer and should be released or retried by the state, a federal judge ordered.

In an 81-page opinion issued Wednesday, U.S. District Judge Malcolm Marsh said new DNA analysis and other evidence raises doubts about whether Lisa Marie Roberts strangled Jerri Lee Williams, a Northeast Portland woman with a history of prostitution and drug use, in May 2002. Williams' naked body was found down a slope from the parking lot at Kelley Point Park, which is at the confluence of the Columbia and Willamette rivers.

That finding alone would not be sufficient to release her, and Marsh stopped short of deeming her "probably innocent" of the crime. But the possibility of her innocence allows him to consider an otherwise-expired claim that her trial lawyers had provided ineffective counsel, the judge wrote. After reviewing the case, he wrote, he agreed that she had been denied her constitutional right to effective counsel.

Multnomah County prosecutors' case against Roberts was built in large part on circumstantial evidence, he wrote.

Roberts had been living with another woman, Terry Collins, in the 7800 block of Southeast 65th Avenue when the two met Williams, Marsh wrote. Roberts and Williams developed a romantic relationship, which sparked a "volatile love triangle," among the three.

Marsh noted a past history of domestic abuse, in which Roberts had choked Collins to the point of unconsciousness and had once repeatedly punched Williams, Marsh wrote. Another witness also reported seeing Roberts slam Williams against a wall. In addition, Collins and others said Roberts had made statements on several occasions threatening to "take care" of Williams and put her "six feet under" and made other comments regarding wanting to hurt one of Collins' girlfriends.

On Saturday, March 25, 2002, Williams called a friend to say she was going to come see her at the Madison Suites Motel on Northeast 82nd Avenue after going to the McDonald's restaurant nearby, Marsh wrote. Roberts said she dropped off Williams sometime between 9 am and 9:30 a.m. at the McDonalds before heading toward Gresham to pick up Collins' daughter, who was going to spend the weekend with her, she said.

Williams' friend never saw her arrive at Madison Suites. Her body was found just before 3 p.m. with a pillowcase near her body.

When questioned, Roberts gave conflicting statements about Williams' plans and if she last saw her heading into McDonalds or going to the motel. She also gave detectives conflicting information for her route to pick up Collins' daughter, saying that she missed exits and had to double back before getting to the right location.

Investigators pulled Roberts' cell phone records, finding that she and Collins' daughter had exchanged three phone calls between 9:38 a.m and 10:27:59 a.m. The third call connected to a cell phone tower in Vancouver, about three miles from Kelley Point Park, the opinion states. Roberts maintained that the closest she would have come would be along Interstate 205 at Marine Drive. That location is about 10 miles from Kelley Point Park.

Medical examiners had collected DNA evidence from Williams' body, including material from under her fingernails and breast as well as sperm collected from vaginal swabs. The sperm did not draw a match when state investigators ran it through a database in 2002.

Police theorized that Roberts had killed Williams at home, placed her body in a sleeping bag with a pillowcase over her head, driven her in a pickup and dumped her body at the park sometime before 10:27 a.m when her call to Collins' daughter bounced off the Vancouver cell tower.

Roberts, then 37, was prepared to go to trial, Marsh wrote, based on statements from her lawyers at the time. But just before trial was to begin, prosecutor Rod Underhill, now Multnomah County District Attorney, shared information with the defense about cell phone evidence he planned to introduce.

Roberts' lawyer, William Brennan, told her the data would pinpoint her location near Kelley Point Park and which direction the call was coming from and advised her to plead guilty, according to the opinion. Brennan has since died.

But technical experts hired for Roberts' federal case countered that cell phone tower data cannot pinpoint a person's location or the direction from which the call is being made. In addition, the experts noted that the prosecution did not consider the wide area that the tower was designed to cover nor other variables such as the call load, network of the tower and the cell phone provider's software all of which could affect which tower handles a person's cell call.

Marsh found that Brennan failed to adequately investigate or hire an expert to evaluate the cell phone tower evidence, and instead relied on the prosecutor's expert.

"Despite the critical importance of the cell tower evidence, Brennan failed to take reasonable steps to collect the relevant data and independently evaluate the reliability of the Verizon technician's preliminary analysis before advising his client to plead guilty to manslaughter," Marsh wrote.

He notes that Roberts would likely have insisted on going to trial, except for her lawyer's failure to evaluate the cell phone data and hire an expert. She was sentenced to 15 years in prison and three years of post-prison supervision and has been serving her time at Coffee Creek Correctional Facility.

Roberts' team offered other evidence as well, including the results of new DNA analysis in 2013 that showed links between the genetic material recovered from Williams' body with two men who knew her.

The defense argued that one of them, who is currently in prison on sex abuse charges, used to live at the Madison Suites Motel had frequently harassed Williams into getting her to prostitute for him, according to Williams' son. Other witnesses offered information about his connection to Williams, and court documents cited by the opinion accuse him of hitting, choking and threatening women.

The state has 90 days to decide whether it wants to retry Roberts.

"We are working to determine all of our options and then we will review each option and make a decision about which is the most appropriate one to pursue," Underhill said in an email.

Federal Public Defender Steve Wax, who argued the habeas corpus appeal in U.S. District Court with Assistant Public Defender Alison Clark, hailed the decision, which came on the same day he was celebrating the launch of the Oregon Innocence Project.